1. Field of the Invention
The present invention relates to a method of and an apparatus for detecting the condition of a crack generated in a rotor of a rotary machine during an operation.
2. Description of the Prior Art
In recent years, as there is an increased demand for larger capacities of power plants such as thermoelectric power plants and nuclear power plants, the capacities of major equipments of these plants such as steam turbines, generators and so forth become larger. Therefore, any accident in the steam turbine or the generator may cause a serious problem such as an interruption of an electric power supply over a wide region or district.
In order to obviate such a problem, it becomes quite important that an abnormality occurring in the turbine or the like is detected at an early stage and a repair and that a replacement of parts be made promptly. The abnormality in such rotary machines is attributable to various causes and develops various symptoms among which an abnormal vibration of a motor of the rotary machine occurs most frequently and often causes serious accidents.
The abnormal vibration of the rotor is often caused by generation of a crack therein. Any crack generated in the rotor of a turbine or a generator tends to grow rapidly to cause a breakdown thereof, because such rotary machines are interrupted frequently in order to adjust a power supply in view of a load demand which varies according to seasons and even in a day.
Hitherto, the detection of the crack generated in the rotor has been made by a non-destructive inspection or the like measure at the time of a non-operation of the rotor, e.g. a fabrication of the rotor or a periodic inspection.
Some proposals have been made for detecting a crack in the rotor during the operation of the rotary machine. However, these proposals necessitate specific additional detecting devices which are generally expensive. Therefore, to provide for early detection of a crack in the rotor so as to avoid a serious accident in the rotary machine, it is necessary either to interrupt the operation of the rotary machine frequently to provide for non-destructive inspection of the rotor, or to provide the additional detecting devices for to the rotary machine. However, in the former case the rate of operation of the rotary machine is decreased. In the latter case the cost of the rotary machine is raised.